干旱胁迫下偏关苜蓿显微结构响应特征研究

以山西地方优良种质--偏关苜蓿(Medicago sativa‘Pianguan’)为材料,采用20% PEG模拟干旱胁迫0, 24, 48, 72 h后,观测根、茎、叶各器官显微结构特征参数。利用单位干旱时间内各显微结构参数相对响应关系及干旱时间与干旱指标实测值关系,获取能够在显微结构尺度上定量评价植物体各组织对干旱胁迫响应关系的干旱指数:干旱响应率(RR)和干旱响应度(RD),旨在为干旱胁迫与细胞响应的其他相关研究提供方法学参考。结果表明:叶片海绵组织厚度和栅栏组织厚度、茎韧皮部厚度和筛管直径及髓腔直径、根直径和表皮厚度分别对干旱胁迫有相对较高的响应特征,其中叶片海绵组织厚度、栅栏组织厚度和茎髓腔直径的响应特征最高。综合响应率和响应度分析得出各器官对PEG的耐受性依次为根> 茎> 叶。

Effect of Drought Stress on Microstructural Characteristic Changes of Medicago sativa ‘Pianguan’

The objective of this study was to provide a methodological reference to other relevant research. The microstructural characteristic changes of leaves, stems, and roots in Medicago sativa ‘Pianguan’ that under drought stress condition were evaluated after 0, 24, 48 and 72 h of 20% PEG treatment. Drought response degree (RD) and response ratio (RR) were calculated based on two equations: one was deduced based on the response of a unit's relative value for the observed microstructural characteristic parameters at unit drought time, and the other was deduced based on the linear relative degree between the raw value of thickness of drought indices and drought time. The results demonstrated that compared with the baseline at 0 h, leaf spongy parenchyma thickness, palisade parenchyma thickness, stem phloem thickness, sieve tube diameter, pith cavity diameter, root diameter, and epidermis thickness had significantly higher response characteristics under drought stress. According to the calculation results, the response characteristics of leaf spongy parenchyma thickness, palisade parenchyma thickness, and stem pith cavity diameter were the highest among all test indices. The results of both RD and RR analyses indicated that roots had the greatest tolerance to PEG, followed by stems and leaves.